Human and animal habitations generate large quantities of wastes. The organic fraction of these wastes often accumulate in the neighborhood of habitations and their decomposition products affect detrimentally the quality of soil, water and air. Meanwhile, the demand for water has gone up and the need to renovate and reuse water has become imperative. In developing countries existing technologies for wastewater renovation are viable only in very large-scale operations and so cost of operation becomes prohibitive and lead to improper functioning and maintenance of plants (Arceivala, S. J., Wastewater Treatment for Pollution control, TMH publications New Delhi, India, 1998). Even the treated water in many cases breed mosquitoes thereby compounding the problem.
Many technologies are available to deal with organic wastes but most of these are energy intensive. Sanitary land filling is becoming unviable due to non-availability of landfill space. In biogas technology investments are large and subsequent liquid effluents consume much energy for disposal and solid product from such processes having low energy value for soil have limited market as fertilizer. Most current technologies face problems of acidity, culture fatalities and problems of process waste disposal. Composting has been practiced for over 50 years. However in the composting process bioenergy of the organic waste is lost and therefore the product retains very little energy for use in soil. In view of energy cost of composting operation, low value and low yield of product, the technology becomes useful if disposal is the objective. Organic waste conversion to biomass briquettes is a useful technology but the energy cost of drying and briquetting is high and hence such technology is also unviable in many cases.
Several technologies are available for treatment of organic liquid waste containing chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrogen, phosphorous, suspended solids, bacteria, color, odor etc. The presence of these pollutants in water is a form of toxicity and should therefore be substantially removed. Activated Sludge, Trickling filter, and Oxidation Ponds are examples of technologies currently in operation. All these technologies are energy intensive and viable only in very large scale. They produce residues whose disposal can create problems. Treated water is generally not fish compatible and such water discharged into drinking water sources endanger lives of dependent population (Bhawalkar, U. S., “Vermiculture Bioconversion of Organic Residues”, Ph. D. Thesis, Dept. of Chemical Engineering, IIT Bombay, 1996; Pattanaik B. R., “Processing of Wastewaters in Soil Filters”, Ph.D. Thesis, Dept. of Chemical Engineering, IIT Bombay, 2000). Land treatment of wastewater has been known for long. Here intermittent hydraulic loading of 0.001 m3/m2 per hr. is permissible and treated water is not easy to recover for reuse. Root zone treatment technology is similar to land treatment methods and have similar requirement and features (Nivens, Jr., U.S. Pat. No. 6,264,838, “Onsite Wastewater Recycling System”). Constructed wetland treatment technology has been in practice in many areas. In this case wetland-rock-aquatic ecology is engaged wherein subsurface flow brings about treatment. Hydraulic loading of 0.001-0.005 m3/m2.hr is observed (Behrends, U.S. Pat. No. 5,863,433, “Reciprocating Subsurface Flow, Constructed wetland for improving Wastewater Treatment”).
Use of surface dwelling redworm Eisenia foetida in vermifilters and Vermicomposting is known (Lee, K. E., Earthworms—Their ecology and relationship with soils & land use, Academic Press, NY (1985)). However, there are major drawbacks of such processes and formulations leading to low yield of vermicompost. Moreover, it requires well-macerated excreta, preferably animal excreta, containing 1 percent or more protein nitrogen and 70 percent moisture. Also, there are problems of maintaining them in the filter. This is because they cannot live in their own excreta and as conditions arising from accumulation of waste products become adverse they migrate away. (Bhawalkar, “Vermiculture Bioconversion of Organic Residues”, Ph.D. Thesis, Dept. of Chemical Engineering, IIT Bombay, 1996.; Pattanaik B. R., “Processing of Wastewaters in Soil Filters”, Ph.D. Thesis, Dept. of Chemical Engineering, IIT Bombay, 2000) In order to prevent this migration converted material is to be separated and fresh material is to be added to the process. This leads to low loading rates thereby requiring large space for the vermicomposting process. Culture replacement is also necessary. In view of the generated acidic environment abnormal bio indicators of acidic environment do appear and the use of other chemical pest control measures become necessary. When the acidity becomes very high it becomes essential to unearth the entire space and prepare the place afresh leading to long turnover times, loss of productivity, etc. Such redworm cultures not being native to healthy soils their disposal becomes problematic. Other issues related to the use of Eisenia foetida (all surface dwelling varieties) are sudden loss of culture and pest incidence. (Bhawalkar U. S., Vermiculture bioconversion of Organic Residues, Ph.D. thesis, IIT Bombay 1996; Pattanaik, B. R., Waste Water Processing in Soil Filters, Ph.D. thesis, IIT Bombay, 2000). In general, available technologies do not use soil system because they tend to choke and become non-functional.